Artificial colors are also known as certifiable colors because they are required to undergo certification by the Federal Drug Administration (FDA) prior to usage in food or drugs. Artificial colors such as FD&C Yellow No. 6, FD&C Blue No. 1, and FD&C Red No. 40 provide a wide spectrum of colors for use in foods, beverages, drugs, and cosmetics. However, both consumers and manufacturers have created a demand for natural colorant alternatives. Natural colors are exempt from the certification process, but still undergo safety reviews by the FDA. The FDA has created a list of natural colorants that have been approved for use in foods. This list includes red cabbage, beet juice or powder, carmine, grape skin extract, and color extractives from grapes.
Many of the sources of natural food colorants contain a chemical called anthocyanins which belong to a larger class of compounds called flavonoids. Anthocyanins are composed of aglycone (anthocyanidin), sugar and may also include organic acids. Anthocyanins are water soluble pigments that occur naturally in a variety of plants, vegetables, flowers, and grains. Anthocyanins can be found in high levels in plant or plant products such as grape juice, grape skin extract, elderberry, purple carrot, red radish, and red cabbage.
As a group, anthocyanins exhibit diverse color qualities at different pH levels. For example, at a pH of about 3, anthocyanins will exhibit a red color. However, when placed in a more basic environment, at a pH of 8 for example, the anthocyanin may be green or blue. The color intensity of anthocyanins also varies with pH, with the highest color intensity exhibited at pH values less than 4. However, anthocyanin extracts are typically unstable at a pH higher than 6. It is an object of the present invention to provide stabilized blue and green colorants which retain their hue when used as a colorant in slightly acidic, neutral, and/or basic conditions.
Although generally more expensive than other sources of anthocyanins, red cabbage extracts are often used in natural colorants. Red cabbage comprises fifteen anthocyanins. These fifteen anthocyanins all have cyanidin as the aglycone and glucose as the sugar. Red cabbage anthocyanins comprise the organic acids ferulic and coumaric to produce acylated anthocyanins. As compared to most other anthocyanin extracts, the red cabbage extract shows improved stability when exposed to heat or light. This improved stability is due to the presence of acylated anthocyanins. Red cabbage extract also exhibits a high tinctorial strength compared to other anthocyanin-based colors.
U.S. Patent Application Publication No. 2003/0082281 by Kohler et al describes a blue colorant that is formed by the combination of an anthocyanin, such as red cabbage, and an aluminum compound. Kohler et al discloses an aluminum lake or a blue lake in which a base is added to raise the pH to the range of 5 to 9 to form a precipitate. However, no reference is made to the formation of blue dye colorant that is water soluble and is created without forming a precipitate or raising the pH of the colorant above 4.5.
While many colors are available in a natural colorant, the colors blue and green are noticeably absent in this group. Accordingly, a natural blue colorant that can be used in a wide variety of food, drug and cosmetic applications would be considered useful.